1. Field of the Invention
The present invention generally relates to suspending agents, cement compositions and methods of cementing, and more particularly, to cement compositions which do not settle when exposed to high temperatures and high pressures.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized in forming structures above and below ground. In forming such structures, a hydraulic cement composition is pumped into a form or other location to be cemented and allowed to set therein. Generally, the cement composition must not settle and separate prior to setting.
In the construction and repair of wells such as oil and gas wells, hydraulic cement compositions are pumped into locations in the wells to be cemented and allowed to set. In primary well cementing, a hydraulic cement composition is pumped into the annular space between the walls of the well bore and the exterior surfaces of a pipe string disposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The cement sheath physically supports and positions the pipe string in the well bore and bonds the exterior surfaces of the pipe string to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented.
In the primary cementing of high temperature and high pressure wells, hydraulic cement compositions are exposed to the high temperatures and pressures during pumping for long periods of time and as a result, the cement compositions often become thin and the heavier components of the compositions settle and separate whereby the set cement has density variations therein and lacks the high strength required. As a result, significant portions of the cement sheath in the annulus between the pipe string and the walls of the well bore do not bond to the pipe string or the walls thereby bringing about leakage and/or blowouts.
Thus, there are needs for improved methods and cement compositions whereby the cement compositions do not settle and do not fail to bond to adjacent surfaces.